1. Field of the Invention
The present invention relates to a printed circuit board, and more particularly, to a printed circuit board for a liquid crystal display device widely used in notebook computers, which is capable of decreasing wireless wide area network (WWAN) noise.
2. Discussion of the Related Art
With the progress of an information-dependent society, the demand for various display devices has increased. To meet such a demand, efforts have recently been made to research flat panel display devices such as liquid crystal display (LCD) devices, plasma display panels (PDPs), electro-luminescent display (ELD) devices, vacuum fluorescent display (VFD) devices, and the like. Some types of such flat panel display devices are being practically applied to various appliances for display purposes.
In particular, LCDs have been widely used in association with mobile image display devices because they have the advantages of superior picture quality, lightness, thinness, and low power consumption. Various applications of LCDs are being developed in association not only with mobile image display devices, such as monitors of notebook computers and other computers, but also monitors of TVs, or other monitors. Thus, such an LCD may be a most representative flat panel display device.
In particular, notebook computers, in which portability is an important feature, different from desktop computers mainly used in fixed spaces such as offices or schools, mainly use an LCD device to output image information.
Such an LCD device includes an LCD panel constituted by two substrates assembled to face each other via a liquid crystal layer interposed between the substrates, a backlight unit for irradiating light to the LCD panel, to enable rendering of an image, and a circuit for supplying signals to drive the LCD panel. The circuit includes a printed circuit board (PCB), on which a timing controller for supplying signals received from a system to the LCD panel in a re-arranged state, and other components are mounted.
The PCB not only functions as lines for supplying signals, but also functions to mechanically fix the timing controller and other components, for the mounting thereof. Such a PCB is classified, in accordance with the structure thereof, into a single layer PCB, in which a copper thin film layer is formed only on one surface of a resin layer, a dual layer PCB, in which copper thin film layers are formed on opposite surfaces of a resin layer, respectively, and a multilayer PCB, in which resin layers and copper thin film layers are alternately laminated. Recently, the multilayer PCB has been mainly used in that an increased number of signal lines can be integrated in the multilayer PCB in accordance with the development of laminating techniques.
The interest in a ubiquitous environment enabling access to a network, such as the Internet, without regard to location and time is increasing. As a result, the utilization of notebook computers, which are very portable, is also increasing.
Also, various techniques for enabling access to a wireless communication network, in particular, a wireless wide area network (WWAN), using a notebook computer are being developed.
However, when a desired task is conducted under the condition in which access to a WWAN is obtained using a notebook computer, it is very important to decrease noise generated due to interference between signals generated from the notebook computer and signals or electromagnetic waves generated from other electronic appliances arranged around the notebook computer, or internal signal interference occurring in the notebook computer.
The LCD device, which is used to output image information from the notebook computer, has a problem in that electromagnetic waves are generated from an inverter for driving the backlight unit. Furthermore, the LCD device generates signal interference when the notebook computer accesses and communicates with a WWAN, due to various signals supplied to various components mounted on the PCB, for example, the timing controller, and signal lines formed on the PCB. As a result, there is a problem in that WWAN noise is generated.
The WWAN noise degrades the quality of wireless communication. In a severe case, the WWAN noise applies a load to hardware, thereby degrading the reliability of the associated equipment.